ReviseNow1998 - Revise Now

PAPER 1

SECTION A

Answer all questions from this section.

1. RCO₂H is a weak acid

(a)Write equation for the ionisation of the weak acid RCO₂H in water

……………………………………………………………………………………………………………………………………………………………………………………………………

(b)Write expression for the ionisation constant Ka for the acid

2. Name one reagent that can be used to distinguish between each of the following pairs of compounds. In each case state what would be observed if each member of the pair is treated with the reagent.

(b) CH₃CH₂NH₂and (CH₃CH₂)₂NH

3. The table below shows the rates of the reaction between substances A and B at different concentrations.

Experiment	Initial concentration in mol dm-3 of	Initial rate of reaction in mol dm-3 s-1
	A B
1	0.50 0.50	2.0x10^-2
2	1.00 0.50	8.0x10^-2
3	1.00 1.00	16.0x10^-2

(a)Determine

(i)The order of reaction with respect to A and B

A……………………………………………………………………………………………………………………………………………………………………………………………………

B……………………………………………………………………………………………………………………………………………………………………………………………………

(ii)the overall order of reaction

(b) (i) write an expression for the rate of reaction

(ii)Calculate the rate constant for the reaction and state the units

4. Equation for some half cell reactions are given below:

chem_1998_no_4_paper_1

(a)Write the convention for the cell

(b)Write equation for the overall reaction

(c)Calculate the cell voltage

5. Draw the molecular structures of the following compounds and in each case name the shape of the molecule.

(a)Sulphurtrioxide,SO₃

(b)Trichloromethane,CHCL₃

(d)Phosphite,PH₃

6. (a)Write an expression for pH.

(b) (i) Calculate the pH of a 0.05M solution of sodium hydroxide

(Kw=1x10^-14M)

Give a reason for your answer

7. When 0.13g of a chloride of iron was vaporised at 600K and 1 atmosphere pressure 20cm³ of vapour was formed.

(a)Calculate the relative mass of iron chloride

(b) (i) Determine the molecular and formula of the iron chloride

(ii)Write the structural formulae of the iron chloride

8.(a) But-2-ene van be prepared from butan-2-ol and phosphoric acid

(i)State the conditions for the reaction

(ii)Write a mechanism for the reaction

(b)But-2-ene was passed through acidified potassium permanganate solution

(i)State what was observed

(ii)Write equation for the reaction

(iii)State the change in the oxidation state of manganese

9. (a)In the complex Co(NH₃)₅(H₂O)Cl₃

(i)State the oxidation state of cobalt

(ii)Give the name of the complex

(b)State three factors that affect of complex formation in transition metals

SECTION B

Answer six questions from this section

10. Complete each of the equations and in each case write a mechanism for the reaction

(a)

(b) chem_1998_no_10_b_paper_1

11. Explain briefly the following characteristics

(a) Ice has a lower density than water.

(b) The boiling point of HF is higher than that of HCL.

12. The diagram below shows successive ionisation energies for an element X showing removal of all electrons.

chem_16

(a)Giving reasons state

(i) the group of element X

(ii) the period of element X

(iii)Identify element X

(b) Explain the sudden increase in the energy required to remove electron E

(d) Explain what would be the sign of energy change if an electron was added to X to give X

(ii)How would you expect it to affect the size of X?

(e) Explain giving reasons whether you would predict X to form compounds in the +1 oxidation state.

13.1 mole of hydrogen iodide gas at 25⁰C was introduced into a container of volume 20.0 litres.

(a) Calculate the pressure of the gas, assuming ideal behaviour (1 mole of an ideal gas occupies 22.4 litres under standard conditions).

(b) The sample of hydrogen iodide, considered above was raised to a temperature at 300⁰C and it partially decomposed into hydrogen and iodine gases. At equilibrium,1mole iodine was found to be present.

(i) Write an equation for the decomposition

(ii) Calculate the pressure of the equilibrium mixture at 300⁰C.assuming no change in volume.

(iii) Calculate the equilibrium constant at 300⁰C.

(c) ∆H_f⁰(HI_(g))= +26.5kj mol^-1.Explain giving reasons how you would expect equilibrium constant to change with temperature

14. (a) Rubber is a natural polymer whose monomer is 2-methylbutan-1,3-diene

Write the structure of

(i)the monomer of rubber

(ii)the structural formula of rubber

(b) (i) Briefly explain how rubber is vulcanised

(ii)State the purpose of vulcanising rubber

(d) Name one other natural polymer

15. The table below shows the temperature rise when various volumes of 2M sulphuric acid were added to 60cm³ of about 2M sodium hydroxide an in each case the total volume made up to 120cm³ with water.

Experiment	1	2	3	4	5	6
Volume of NaOH(cm³)	60	60	60	60	60	60
Volume of 2M H₂SO₄(cm³)	5	10	20	25	30	40
Volume of water(cm³)	55	50	40	35	30	20
Temperature rise(⁰C)	4.8	6.9	9.1	10.1	10.1	10.0

(a) Plot a graph of temperature rise against volume of sulphuric acid added

CHEM_10

(b)From the graph determine the highest temperature rise.

(the density of solution is 1 kg dm-3 and specific heat 4.2kj/kg/K)

16. (a)When red lead,Pb3O4 was reacted with nitric acid a solid was formed

Write the equation for the reaction.

(b)The mixture from (a) was filtered and the residue wormed with concentrated hydrochloric acid.

(i)What was observed? Explain your answer.

(ii)Write equation for the reaction.

(i) To the first part was added aqueous potassium iodide. State what was observed and write equation for the reaction

…………………………………………………………………………………………………………………………………………………………………………………………………

(ii) The second part was evaporated to dryness and heated strongly. Explain what was observed and write the equation for the reaction

17. The elements contained in the third short period of the periodic table given in the alphabetical order, are aluminium, argon, magnesium, phosphorus, silicon, sodium, sulphur.

(a) In the table given below write the formula of hydrides formed by the elements listed, state the oxidation states (or valency) of the elements in these hydrides and classify the bonding in the hydrides as ionic or covalent.

Elements	Formula of hydride	Oxidation (of valency)of the elements in the hydride	Type of bonding
Aluminium
Chlorine
Magnesium
Phosphorus
silicon

(b)The hydrides formed by sodium and sulphur were separately shaken with water

Write the equation to show the reaction which took place if any with

(i)sodium hydride

(ii)sulphur hydride

PAPER 2

SECTIONA

Answer three questions from this section

1. (a)Describe using equations the reactions of zinc with

(i)air

(ii)Water

(iii)Sodium hydroxide

(b) (i)Explain why zinc is not considered a typical transition metal

(ii)State three ways in which the chemistry of zinc is similar to that of magnesium

(ii)Write equation(s) for the reaction that takes place in (c) (i).

2. The boiling points of the hydrides of group(VII) elements are given in the table below.

compound	HF	HCl	HBr	Hl
B.P(⁰C)	+19.9	-85.0	-66.7	-35.4

(a) Explain the trend in boiling points of hydrides.

(b) Giving reasons suggest the trend in the acid strength of hydrides.

(c) Using equations where possible explain what happens when concentrated sulphuric acid is mixed with each of the hydrides.

(d) (i)Arrange the following compounds in order of their increasing acid strength. HCIO, HCIO₂, HCIO₃, HCIO_4.

(ii)Explain your answer in d(i)

3. (a)Explain the following terms

(i)Solubility

(ii)Eutectic mixture

(b)The equilibrium diagram foe the sodium nitrate water system is shown below

(i) State what lines DE and EF represent.

(ii) Determine the percentages of sodium nitrate at points A B and C.

(iii)Name the substances present at A, B, C and E.

(ii) State two reasons why eutectic mixtures are not compounds.

4. Name the class of compounds to which each pair of the following substances belong and name each substance.

chem_1998_no_4_paper_2

For each pair of compounds give one test to distinguish them. In each case describe the observations expected and name the products.

SECTION B

Answer two questions from this section.

5. (a) (i) What is structural isomerism?

(ii) Describe the three types of structural isomerism giving a suitable example in each case.

(b) A compound has the following formulaC₃H₆Cl₂.write down the three possible structures for the compound.

(c) Describe the reaction of one of the isomers of C₃H₆Cl₂ with sodium hydroxide and write the mechanism of the reaction.

6. (a) (i)what is the chemical nature of all soaps?

(ii) Give the chemical name of an example of a soap

(iii) What do you understand by the term synthetic detergent?

(iv) Explain clearly how soaps or detergents remove grease particles during the process of washing

(v) Give one advantage and disadvantage of detergents

(vi) Give the chemical process that occur during the manufacture of

-soaps

-detergents

Indicate clearly which raw materials are used in each case.

(b) (i) what are the constituents of crude oil

(ii) How are these separated

(iii) Briefly explain cracking and state its use in petroleum industry.

7. (a)Explain what is meant by the term ideal solution.

(b) Propanone was mixed with trichloromethane.

(i) State what was observed. Explain your answer

(ii) Sketch a labeled diagram for the vapour pressure-composition for the mixture of propanone and trichloromethane.(the boiling point of propanone is lower than that of trichloromethane).

(iii) Describe what would happen if a mixture of trichloromethane and propanone was fractionally distilled.

(c)The boiling point of a solution containing 2.8g of a compound Z in 20g of water is 100.2⁰C at standard pressure(b.p of water is 100⁰C at standard pressure).

(i) Explain how the solute affects the boiling point of water

(ii) Calculate the relative molecular mass of Z

(K=0.52⁰C mol^-1 per 1000g).

8. Explain each of the following observations (use equations to illustrate your answer where necessary.

(a)When aqueous sodium carbonate is added to zinc chloride solution a precipitate is formed whereas when carbonate solution is added to acidified zinc chloride solution no precipitate is formed.

(b) A mixture of water (boiling point 100⁰C) and benzene (boiling point 80⁰C)boils at 70⁰C at 1 atmosphere pressure.

(d) Methanoic acid reacted with ammoniacal silver nitrate solution whereas ethanoic acid does not.

(e)When dilute hydrochloric acid is added to a solution of lead (II) ethanoate, a white precipitate is formed. The precipitate is soluble in excess concentrated hydrochloric acid.

CHEMISTRY 1998